1. Field of the Invention
The present invention relates to a device and method of controlling the operation of a robot apparatus having at least a plurality of movable portions, and, more particularly, to a device and method of controlling the operation of a robot apparatus to be used in various expected environments.
Even more particularly, the present invention relates to a device and method of controlling the operation of a robot apparatus which autonomously and internally overcomes an abnormal state when the abnormal state is detected in the robot apparatus. Still even more particularly, the present invention relates to a device and method of controlling the operation of a robot apparatus which autonomously overcomes combined and detected abnormal states with consistency.
2. Description of the Related Art
A robot is a mechanical device which moves like a human being by making use of electric and magnetic actions. The term “robot” is said to be derived from the Slavic word “ROBOTA” (slavish machine). In our country, the widespread use of robots began at the end of the 1960s, many of which were industrial robots, such as manipulators and conveyance robots, used, for example, for the purpose of achieving automatic production operations in factories without humans in attendance.
In recent years, advances have been made in the research and development of legged mobile robots which are designed using as a model the motion and mechanism of the body of an animal, such as a human being or an ape, which moves erect using two feet (refer to, for example, Japanese Unexamined Patent Application Publication No. 13-129775). Bipedal movement in an erect posture is unstable compared to, for example, crawling or movement using four or six legs. Therefore, in this case, the posture and walking are difficult to control. However, bipedal movement in an erect posture is excellent in that it is a flexible movement. Therefore, robots capable of such a movement can, for example, move along a rough walking surface of a working path, such as a surface having obstacles, or move along a discontinuous surface, such as moving up and down steps or a ladder.
Legged mobile robots which reproduce the movements and bodily mechanisms of a human being are called humanoid robots. Humanoid robots help people in life, that is, help them in various human activities in situations in living environments and in various other situations in everyday life.
Most of the working spaces and living spaces of human beings are formed in accordance with the behavioral mode and the body mechanism of a human being which walks erect using two legs. For moving present mechanical systems using wheels or other such driving devices as mover, many obstacles exist. Therefore, it is preferable that the movable range of the robot be about the same as that of human beings in order for the mechanical system, that is, the robot to carry out various human tasks in place of them, and to deeply penetrate the living space of human beings. This is the reason why there are great expectations for putting a legged mobile robot into practical use.
Posture stability control of legged mobile robots is often achieved by making use of ZMP (zero moment point) as a norm for determining the degree of walking stability. ZMP referred to here is a point on a floor surface where the moment caused by reaction force of the floor while the robot is walking is zero. The norm for determining the degree of walking stability by ZMP is based on D'Alembert's principle in which gravitation and inertial force from a walking system to a floor surface and their moments balance floor reaction force and floor reaction moment from the floor surface to the walking system. The inference in terms of dynamics is that there is a point, that is, a ZMP where a pitch axis moment and a roll axis moment are zero within a side of a supporting polygon defined by the floor surface and the points of contact of the sole with the floor (refer to, for example, “Legged Locomotion Robots” by Miomir Vukobratovic, and “Walking Robot and Artificial Leg” by Ichiro Kato et al. (Nikkann Kogyou Shinbun-sha)).
A target ZMP control is successfully achieved in an actual robot by planning its motion so that it moves in a dynamically balanced manner every instant. According to a bipedal walking pattern based on ZMP, the points where the soles contact the floor can be previously set, so that, for example, it is easy to consider kinematic constraints on the ends of the feet in accordance with the shape of the floor surface. When ZMP is used as a norm for determining the degree of stability, a trajectory instead of force is used as a target value for controlling movement. Therefore, technically speaking, the probability putting ZMP into practical use is increased.
Here, a tall legged mobile robot is assumed as being used in various environments regardless of whether the ground is level or rough, so that it may be used in many circumstances where a control system of the body of the robot deviates from guaranteed operation conditions. Therefore, it is more probable that an abnormal state occurs in an unexpected circumstance in such a robot than in other mechanical devices. Consequently, it is desirable that the robot internally detects an abnormal state and autonomously overcomes the detected abnormal state. Two or more abnormal states may occur in combination. It is necessary for the robot to overcome the individual abnormal states with consistency.
Many related robot technologies attach importance to functions. Therefore, most related robot technologies do not provide safety functions with respect to the external world. For example, although industrial robots provide many safety measures, they do not internally have safety functions, that is, safety functions are primarily provided outside the robot, such as providing a spatial threshold so that a person does not enter its movable section or providing an emergency stop switch (refer to, for example, Japanese Unexamined Patent application Publication No. 2001-38661).
If it is assumed that a robot, such as an entertainment robot, will be used in households, it will become increasingly necessary for the robot to act so as not to be adversely affected by the external world such as the environment or the user and so as to reduce injuries of and the load on the robot itself. In other words, the robot needs to internally detect any abnormal state and quickly and autonomously overcome the abnormal state.
Here, if a human being touching something hot is taken as an example, the robot needs to have a function that overcomes the abnormal state at an early stage by instinctively withdrawing the hand rather that withdrawing the hand after rationally feeling that that something is hot.